Transcript Chapter 16: Neural Integration II: The Autonomic Nervous System

Chapter 16:
Neural Integration II:
The Autonomic Nervous
System and Higher-Order
Functions
Somatic Nervous System (SNS)
• Operates under conscious control
• Seldom affects long-term survival
Autonomic Nervous System
(ANS)
• Operates without conscious instruction
• Coordinates systems functions:
– cardiovascular
– respiratory
– digestive
– urinary
– reproductive
Organization Similarities
of SNS and ANS
Figure 16–2
Organization Similarities
of SNS and ANS
• Are efferent divisions
• Carry motor commands:
– SNS controls skeletal muscles
– ANS controls visceral effectors
PLAY
The Organization of the Somatic and
Autonomic Nervous Systems
The SNS
Figure 16–2a
The SNS
• Motor neurons of central nervous system
• Direct control over skeletal muscles
The ANS
Figure 16–2b
The ANS
• Motor neurons synapse on visceral motor
neurons in autonomic ganglia
• Ganglionic neurons control visceral
effectors
Integrative Centers
• For autonomic activity in hypothalamus
• Neurons comparable to upper motor
neurons in SNS
Visceral Motor Neurons
• In brain stem and spinal cord, are known
as preganglionic neurons
• Part of visceral reflex arcs
Preganglionic Fibers
• Axons of preganglionic neurons
• Leave CNS and synapse on ganglionic
neurons
Autonomic Ganglia
• Peripheral ganglia
• Contain many ganglionic neurons
• Ganglionic neurons innervate visceral
effectors:
– cardiac muscle
– smooth muscle
– glands
– adipose tissues
Postganglionic Fibers
• Axons of ganglionic neurons
• Begin at autonomic ganglia:
– extend to peripheral target organs
Somatic or Visceral
Sensory Information
• Trigger visceral reflexes
• Motor commands of reflexes distributed by
ANS
Motor Commands
• May control activities of target organs
• May alter ongoing activity
• Changes in visceral activity:
– postganglionic fibers release
neurotransmitters
Sympathetic Division
• Does not “Kick in” only during exertion,
stress, or emergency (common
misconception)
• Some aspects of the system are
functioning in visceral reflexes for normal
activity. (pupil dilation and water balance,
for instance)
Parasympathetic Division
• Controls during resting conditions
• Tends to conserve energy
• Allows for “quiet functions” (e.g. digestion,
defecation, etc.)
Divisions of the ANS
• 2 divisions may work independently:
– some structures innervated by only 1 division
• 2 divisions may work together:
– each controlling one stage of a complex
process
Sympathetic Division
• Preganglionic fibers (thoracic and superior
lumbar) synapse in ganglia near spinal
cord
• Preganglionic fibers are short
• Postganglionic fibers are long
ANS: Sympathetic Division
Figure 16–3
Fight or Flight
• Sympathetic division readies body for
crisis
• Increase in sympathetic activity:
– stimulates tissue metabolism
– increases alertness
7 Responses to Increased
Sympathetic Activity
1.
2.
3.
4.
5.
Heightened mental alertness
Increased metabolic rate
Reduced digestive and urinary functions
Energy reserves activated
Increased respiratory rate and respiratory
passageways dilate
6. Increased heart rate and blood pressure
7. Sweat glands activated
Structure of the
Sympathetic Division
• Preganglionic neurons located between
segments T1 and L2 of spinal cord
• Ganglionic neurons in ganglia near
vertebral column
• Cell bodies of preganglionic neurons in
lateral gray horns
• Axons enter ventral roots of segments
Ganglionic Neurons
• Occur in 3
locations:
– sympathetic chain
ganglia
– collateral ganglia
– adrenal medullae
Figure 16–4
Sympathetic Chain Ganglia
• Are on both sides of vertebral column
• Control effectors:
– in body wall
– inside thoracic cavity
– in head
– in limbs
Sympathetic Chain Ganglia
Figure 16–4a
Collateral Ganglia
• Are anterior to vertebral bodies
• Contain ganglionic neurons that innervate
tissues and organs in abdominopelvic
cavity
Collateral Ganglia
Figure 16–4b
Parasympathetic Division
• Preganglionic fibers originate in brain stem
and sacral segments of spinal cord
• Synapse in ganglia close to (or within)
target organs
• Preganglionic fibers are long
• Postganglionic fibers are short
Rest and Repose
• Parasympathetic division stimulates
visceral activity
• Conserves energy and promotes
sedentary activities
Pattern of Responses to Increased
Levels of Parasympathetic Activity
• Decreased:
– metabolic rate
– heart rate and blood pressure
• Increased:
– salivary and digestive glands secretion
– motility and blood flow in digestive tract
• Urination and defecation stimulation
Enteric Nervous System (ENS)
• Third division of ANS
• Extensive network in digestive tract walls
• Complex visceral reflexes coordinated
locally
• Roughly 100 million neurons
• All neurotransmitters are found in the brain
The Adrenal Medullae
Figure 16–4c
Modified Sympathetic Ganglion
• At the center of each adrenal gland in area
known as adrenal medulla
• Very short axons
• When stimulated, release
neurotransmitters into bloodstream (not at
synapse)
• Functions as hormones affect target cells
throughout body
Fibers in Sympathetic Division
• Preganglionic fibers:
– are relatively short
– ganglia located near spinal cord
• Postganglionic fibers:
– are relatively long, except at adrenal medullae
• Ventral roots of spinal segments T1–L2
contain sympathetic preganglionic fibers
Ventral Roots
• Give rise to myelinated white ramus
• Carry myelinated preganglionic fibers into
sympathetic chain ganglion
• May synapse at collateral ganglia or in
adrenal medullae
Preganglionic Fibers
• 1 preganglionic fiber synapses on many
ganglionic neurons
• Fibers interconnect sympathetic chain
ganglia
• Each ganglion innervates particular body
segment(s)
Postganglionic Fibers
• Paths of unmyelinated postganglionic
fibers depend on targets
Sympathetic Innervation
PLAY
Figure 16–5
The Distribution of Sympathetic Innervation
Sympathetic Chain
•
•
•
•
•
3 cervical ganglia
10–12 thoracic ganglia
4–5 lumbar ganglia
4–5 sacral ganglia
1 coccygeal ganglion
Preganglionic Neurons
• Limited to spinal cord segments T1–L2:
– white rami (myelinated preganglionic fibers)
– gray rami (unmyelinated postganglionic fibers)
Rami
• Only spinal nerves T1–L2 have white rami
• Every spinal nerve has gray ramus:
– that carries sympathetic postganglionic fibers
for distribution in body wall
Postganglionic
Sympathetic Fibers
• In head and neck leave superior cervical
sympathetic ganglia
• Supply the regions and structures
innervated by cranial nerves III, VII, IX, X
Abdominopelvic Viscera
• Receive sympathetic innervation via
sympathetic preganglionic fibers
• Synapse in separate collateral ganglia
Splanchnic Nerves
• Formed by preganglionic fibers that
innervate collateral ganglia
• In dorsal wall of abdominal cavity
• Originate as paired ganglia (left and right)
• Usually fuse together in adults
Postganglionic Fibers
• Leave collateral ganglia
• Extend throughout abdominopelvic cavity
• Innervate variety of visceral tissues and
organs
Preganglionic Fibers
• From 7 inferior thoracic segments:
– end at celiac ganglion or superior mesenteric
ganglion
• Ganglia embedded in network of
autonomic nerves
• From lumbar segments:
– form splanchnic nerves
– end at inferior mesenteric ganglion
Celiac Ganglion
• Pair of interconnected masses of gray
matter
• May form single mass or many interwoven
masses
• Postganglionic fibers innervate stomach,
liver, gallbladder, pancreas, and spleen
Superior Mesenteric Ganglion
• Near base of superior mesenteric artery
• Postganglionic fibers innervate small
intestine and proximal 2/3 of large
intestine
Inferior Mesenteric Ganglion
• Near base of inferior mesenteric artery
• Postganglionic fibers provide sympathetic
innervation to portions of large intestine,
kidney, urinary bladder, and sex organs
Neurotransmitters of the
sympathetic division
Neuroendocrine Cells
of Adrenal Medullae
• Secrete neurotransmitters epinephrine (E)
and norepinephrine (NE)
• Since they are carried in the blood they
are actually considered hormones
Epinephrine
• Also called adrenaline
• Is 75–80% of secretory output
• Remaining is noradrenaline (NE)
Sympathetic Division
• Can change activities of tissues and
organs by:
– releasing NE at peripheral synapses
– distributing E and NE throughout body in
bloodstream
Crisis Mode
• Entire division responds (sympathetic
activation)
• Are controlled by sympathetic centers in
hypothalamus
• Effects are not limited to peripheral tissues
• Alters CNS activity
5 Effects of Sympathetic
Activation
1.
2.
3.
4.
5.
Increased alertness
Feelings of energy and euphoria
Change in breathing
Elevation in muscle tone
Mobilization of energy reserves
Stimulation of Sympathetic
Preganglionic Neurons
• Releases ACh at synapses with ganglionic
neurons
Cholinergic Synapses
• Use ACh as transmitter
• Excitatory effect on ganglionic neurons
Stimulation of
Ganglionic Neurons
• Releases neurotransmitters at specific
target organs from telodendria
• Form branching network instead of
synaptic knobs
Sympathetic
Varicosities
• Resemble string
of pearls
• Packed with
neurotransmitter
vesicles
Figure 16–6
Chains of Varicosities
•
•
•
•
Formed from postganglionic neurons
Pass along or near surface of effector cells
No specialized postsynaptic membranes
Membrane receptors on surfaces of target
cells
• Release NE
Adrenergic Neurons
• Use NE as neurotransmitter
Varicosities and ACh
• Some ganglionic neurons release ACh
instead of NE
• Are located in body wall, skin, brain, and
skeletal muscles
NE Released by Varicosities
• Affects targets until reabsorbed or
inactivated
• 50–80% of NE is reabsorbed by
varicosities:
– is reused or broken down by MAO
• The rest diffuses out or is broken down by
enzymes
Duration of Effects on
Postsynaptic Membrane
• NE persist for a few seconds
• ACh only for 20 msec
Effects of NE or E Released by Adrenal
Medullae Last longer because:
– bloodstream does not contain MAO or COMT
– most tissues contain low concentrations
2 Classes of
Sympathetic Receptors
• Alpha receptors
• Beta receptors
Norepinephrine
• Stimulates alpha receptors to greater
degree than beta receptors
Epinephrine
• Stimulates both classes of receptors
Localized Sympathetic Activity
• Involves release of NE at varicosities
• Primarily affects alpha receptors near
active varicosities
Generalized
Sympathetic Activation
• Release of E by adrenal medulla
• Affect alpha and beta receptors throughout
body
Stimulation of
Alpha (a) Receptors
• Activates enzymes on inside of cell
membrane
• Alpha-1 (a1)
• Alpha-2 (a2)
Alpha-1 (a1)
• More common type of alpha receptor
• Releases intracellular calcium ions from
reserves in endoplasmic reticulum
• Has excitatory effect on target cell
Alpha-2 (a2)
• Lowers cAMP levels in cytoplasm
• Has inhibitory effect on the cell
• Helps coordinate sympathetic and
parasympathetic activities
Beta () Receptors
• Affect membranes in many organs (skeletal
muscles, lungs, heart, and liver)
• Trigger metabolic changes in target cell
• Changes occur indirectly
• Each is a G protein
• Stimulation increases intracellular cAMP levels
Beta Receptors
• Two types:
– Beta-1 (1) Increases metabolic activity
– Beta-2 (2)
• Causes inhibition
• Triggers relaxation of smooth muscles along
respiratory tract
Beta-3 (3)
• Found in adipose tissue
• Leads to lipolysis, the breakdown of
triglycerides in adipocytes
• Releases fatty acids into circulation
Sympathetic
Postganglionic Fibers
• Mostly adrenergic (release NE)
• A few cholinergic (release ACh)
• Innervate sweat glands of skin and blood
vessels of skeletal muscles and brain
• Stimulate sweat gland secretion and
dilates blood vessels
ACh
• Released by parasympathetic division
• Body wall and skeletal muscles are not
innervated by parasympathetic division
• Both NE and ACh needed to regulate
visceral functions
Nitroxidergic Synapses
• Release nitric oxide (NO) as
neurotransmitter
• Neurons innervate smooth muscles in
walls of blood vessels in skeletal muscles
and the brain
• Produces vasodilation and increased
blood flow
Summary of
Sympathetic Division (1 of 3)
• Includes 2 sets of sympathetic chain
ganglia, 1 on each side of vertebral
column
• 3 collateral ganglia anterior to vertebral
column
• 2 adrenal medullae
• Preganglionic fibers are short because
ganglia are close to spinal cord
Summary of
Sympathetic Division (2 of 3)
• Postganglionic fibers are longer and
stretch to reach target organs
• Single preganglionic fiber may innervate 2
dozen or more ganglionic neurons in
different ganglia
Summary of
Sympathetic Division (3 of 3)
• Preganglionic neurons release ACh; most
postganglionic fibers release NE, few
release ACh or NO
• Effector response depends on second
messengers activated when NE or E binds
to alpha or beta receptors
ANS: The Parasympathetic Division
Autonomic Nuclei
• Are contained in the mesencephalon,
pons, and medulla oblongata:
– associated with cranial nerves III, VII, IX, X
• In lateral gray horns of spinal segments
S2–S4
Ganglionic Neurons
in Peripheral Ganglia
• Preganglionic fiber synapses on 6–8
ganglionic neurons:
– terminal ganglion:
• near target organ
• usually paired
– intramural ganglion:
• embedded in tissues of target organ
• interconnected masses
• clusters of ganglion cells
Pattern of
Parasympathetic Division
• All ganglionic neurons in same ganglion
• Postganglionic fibers influence same
target organ
• Effects of parasympathetic stimulation
more specific and localized
What are the mechanisms of
neurotransmitter release in
the parasympathetic
division?
Parasympathetic
Preganglionic Fibers
• Leave brain as components of cranial
nerves:
– III (oculomotor)
– VII (facial)
– IX (glossopharyngeal)
– X (vagus)
PLAY
The Distribution of Parasympathetic Innervation
Oculomotor, Facial, and
Glossopharyngeal Nerves
• Control visceral structures in head
• Synapse in ciliary, pterygopalatine,
submandibular, and otic ganglia
• Short postganglionic fibers continue to
their peripheral targets
Vagus Nerve
• Preganglionic parasympathetic innervation
to structures in:
– neck
– thoracic and abdominopelvic cavity
– distal portion of large intestine
• Provides 75% of all parasympathetic
outflow
• Branches intermingle with fibers of
sympathetic division
Sacral Segments of Spinal Cord
• Preganglionic fibers carry sacral
parasympathetic output
• Do not join ventral roots of spinal nerves
Pelvic Nerves
• Innervate intramural ganglia in walls of:
– kidneys
– urinary bladder
– portions of large intestine
– sex organs
Parasympathetic Activation
• Centers on relaxation, food processing,
and energy absorption
• Localized effects, last a few seconds at
most
10 Effects of
Parasympathetic Activation
1. Constriction of pupils:
– restricts light entering eyes
2. Secretion by digestive glands:
– exocrine and endocrine
3. Secretion of hormones
4. Changes in blood flow and glandular
activity:
– associated with sexual arousal
5. Increases smooth muscle activity:
– along digestive tract
6. Defecation:
– stimulation and coordination
7. Contraction of urinary bladder:
– during urination
8. Constriction of respiratory passageways
9. Reduction in heart rate:
– and force of contraction
10. Sexual arousal:
– stimulation of sexual glandsSexual arousal:
– stimulation of sexual glands
Parasympathetic Neurons
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•
•
•
All release ACh as neurotransmitter
Effects vary widely
Inactivated by AChE at synapse
Ach is also inactivated by
pseudocholinesterase in surrounding
tissues
2 Types of ACh Receptors
on Postsynaptic Membranes
• Nicotinic receptors
• Muscarinic receptors
Nicotinic Receptors
• On surfaces of ganglion cells (sympathetic
and parasympathetic)
• At neuromuscular junctions of somatic
nervous system
Action of Nicotinic Receptors
• Exposure to ACh causes excitation of
ganglionic neuron or muscle fiber
• Open chemically gated channels in
postsynaptic membrane
Muscarinic Receptors
• At cholinergic neuromuscular or
neuroglandular junctions
(parasympathetic)
• At few cholinergic junctions (sympathetic)
• G proteins
Action of Muscarinic Receptors
• Effects are longer lasting than nicotinic
receptors
• Response reflects activation or inactivation
of specific enzymes
• Can be excitatory or inhibitory
Toxins
• Produce exaggerated, uncontrolled
responses
• Nicotine:
– binds to nicotinic receptors
– targets autonomic ganglia and skeletal
neuromuscular junctions
• Muscarine:
– binds to muscarinic receptors
– targets parasympathetic neuromuscular or
neuroglandular junctions
Nicotine Poisoning
• 50 mg ingested or absorbed through skin
• Symptoms:
– vomiting, diarrhea, high blood pressure, rapid
heart rate, sweating, profuse salivation,
convulsions
• May result in coma or death
Muscarine Poisoning
• Symptoms:
– salivation, nausea, vomiting, diarrhea,
constriction of respiratory passages, low
blood pressure, slow heart rate (bradycardia)
ANS: Adrenergic and
Cholinergic Receptors
Comparing Sympathetic and
Parasympathetic Divisions
• Sympathetic:
– widespread impact
– reaches organs and tissues throughout body
• Parasympathetic:
– innervates only specific visceral structures
Differences between Sympathetic and
Parasympathetic Divisions
Figure 16–9
Summary: Sympathetic and
Parasympathetic Divisions
Table 16-2
Dual Innervation
• Most vital organs receive instructions from
both sympathetic and parasympathetic
divisions
• 2 divisions commonly have opposing
effects
Summary:
Comparing
Sympathetic and
Parasympathetic
Divisions
Table 16-3 (1 of 2)
Summary: Comparing
Sympathetic and
Parasympathetic Divisions
Table 16-3 (2 of 2)
Anatomy of Dual Innervation
• Parasympathetic postganglionic fibers
accompany cranial nerves to peripheral
destinations
• Sympathetic innervation reaches same
structures by traveling directly from
superior cervical ganglia of sympathetic
chain
Structure: Autonomic Plexuses
• Nerve networks in the thoracic and
abdominopelvic cavities:
– are formed by mingled sympathetic
postganglionic fibers and parasympathetic
preganglionic fibers
• Travel with blood and lymphatic vessels
that supply visceral organs
6 Autonomic Plexuses
1.
2.
3.
4.
5.
6.
Cardiac plexus
Pulmonary plexus
Esophageal plexus
Celiac plexus
Inferior mesenteric plexus
Hypogastric plexus
The Autonomic Plexuses
Figure 16–10
Autonomic Motor Neurons
• Maintains resting level of spontaneous
activity
• Background level of activation determines
autonomic tone
Autonomic Tone
• Is an important aspect of ANS function:
– if nerve is inactive under normal conditions,
can only increase activity
– if nerve maintains background level of activity,
can increase or decrease activity
Autonomic Tone
and Dual Innervation
• Significant where dual innervation occurs:
– 2 divisions have opposing effects
• More important when dual innervation
does not occur
Visceral Reflexes
ANS
• Simple reflexes from spinal cord provide
rapid and automatic responses
• Complex reflexes coordinated in medulla
oblongata
Medulla Oblongata
• Contains centers and nuclei involved in:
– salivation
– swallowing
– digestive secretions
– peristalsis
– urinary function
• Regulated by hypothalamus
Hypothalamus
• Interacts with all other portions of brain
Enteric Nervous System
• Ganglia in the walls of digestive tract
contain cell bodies of:
– visceral sensory neurons
– interneurons
– visceral motor neurons
• Axons form extensive nerve nets
• Control digestive functions independent of
CNS
Characteristics of
Higher-Order Functions
• Require cerebral cortex
• Involve conscious and unconscious
information processing
• Not part of programmed “wiring” of brain
• Can adjust over time
Memories
Stored bits of information gathered through
experience
• Declarative memory
– Facts
• Skill Memory
– Learned motor behaviors
– Incorporated at unconscious level with
repetition
– Programmed behaviors stored in appropriate
area of brain stem
Short & Long Term Memories
Short Term
• Information that can be recalled
immediately
• Contain small bits of information
Long Term
• Can last a life time
2 Types of Long-Term Memory
• Secondary memories fade and require
effort to recall
• Tertiary memories are with you for life
Long-Term Memories
• Most stored in cerebral cortex
• Conscious motor and sensory memories
referred to association areas
Memory Storage
Brain Structures and Memory
• Amygdaloid body and hippocampus:
– are essential to memory consolidation
Damage to the Hippocampus
• Inability to convert short-term memories to
new long-term memories
• Existing long-term memories remain intact
and accessible
Occipital and Temporal Lobes
• Special portions crucial to memories of
faces, voices, and words
“Grandmother cells”
• Specific neuron activated by combination
of sensory stimuli associated with
particular individual (grandmother)
Memories Stored In
•
•
•
•
•
Visual association area
Auditory association area
Speech center
Frontal lobes
Related information stored in other
locations
– if storage area is damaged, memory will be
incomplete
Memory Consolidation
at Cellular Level
• Involves anatomical, physiological
changes in neurons, synapses
Increased
Neurotransmitter Release
• Frequently active synapse increases the
amount of neurotransmitter it stores
• Releases more on each stimulation
• The more neurotransmitter released, the
greater effect on postsynaptic neuron
Facilitation at Synapses (1 of 2)
• Neural circuit repeatedly activated
• Synaptic terminals begin continuously
releasing neurotransmitter
• Neurotransmitter binds to receptors on
postsynaptic membrane
Facilitation at Synapses (2 of 2)
• Produce graded depolarization
• Brings membrane closer to threshold
• Facilitation results affect all neurons in
circuit
Formation of Additional
Synaptic Connections
• Neurons repeatedly communicating
• Axon tip branches and forms additional
synapses on postsynaptic neuron
• Presynaptic neuron has greater effect on
transmembrane potential of postsynaptic
neuron
Memory Engram
• Single circuit corresponds to single
memory
• Form as result of experience and
repetition
Factors of Conversion of short
to long term memory
• Nature, intensity, and frequency of original
stimulus
• Strong, repeated, and exceedingly
pleasant or unpleasant events likely
converted to long-term memories
NMDA (N-methyl
D-aspartate) Receptors
•
•
•
•
•
Linked to consolidation
Chemically gated calcium channels
Activated by neurotransmitter glycine
Gates open, calcium enters cell
Blocking NMDA receptors in hippocampus
prevents long-term memory formation
States of Consciousness
• Many gradations of both states
• Degree of wakefulness indicates level of
ongoing CNS activity
• When abnormal or depressed, state of
wakefulness is affected
2 types of Sleep
• Characteristic patterns of brain wave activity
– deep sleep
– REM
Figure 16–14a
Deep Sleep
•
•
•
•
Also called slow wave sleep
Entire body relaxes
Cerebral cortex activity minimal
Heart rate, blood pressure, respiratory
rate, and energy utilization decline up to
30%
Rapid Eye Movement (REM)
Sleep
• Active dreaming occurs
• Changes in blood pressure and respiratory rate
• Less receptive to outside stimuli than in deep
sleep
• Muscle tone decreases markedly
• Intense inhibition of somatic motor neurons
• Eyes move rapidly as dream events unfold
Nighttime Sleep Pattern
Significance of Sleep
• Has important impact on CNS
• Minor changes in physiological activities of
organs and systems
• Protein synthesis in neurons increases
during sleep
• Extended periods without sleep lead to
disturbances in mental function
Arousal
• Awakening from sleep
• Function of reticular formation
Reticular Activating
System (RAS)
• Important brain stem component
• Diffuse network in reticular formation
• Extends from medulla oblongata to
mesencephalon
Reticular
Activating
System
(RAS)
Figure 16–15
Ending Sleep
• Any stimulus activates reticular formation
and RAS
• Arousal occurs rapidly
• Effects of single stimulation of RAS last
less than a minute
Regulation of
Awake–Asleep Cycles
• Involves interplay between brain stem
nuclei that use different neurotransmitters
• Group of nuclei stimulates RAS with NE
and maintains awake, alert state
• Other group promotes deep sleep by
depressing RAS activity with serotonin
• “Dueling” nuclei located in brain stem
Drugs and Clinical
Considerations
Lysergic Acid Diethylamide
(LSD)
• Powerful hallucinogenic drug
• Activates serotonin receptors in brain
stem, hypothalamus, and limbic system
Serotonin
• Compounds that enhance effects also
produce hallucinations
• Compounds that inhibit or block action
cause severe depression and anxiety
• Variations in levels affect sensory
interpretation and emotional states
Fluoxetine (Prozac)
• Slows removal of serotonin at synapses
• Increases serotonin concentrations at
postsynaptic membrane
• Classified as selective serotonin reuptake
inhibitors (SSRIs)
• Other SSRIs:
– Celexa, Luvox, Paxil, and Zoloft
Parkinson’s Disease
• Inadequate dopamine production causes
motor problems
Huntington’s Disease
• Destruction of ACh-secreting and GABAsecreting neurons in basal nuclei
• Symptoms appear as basal nuclei and
frontal lobes slowly degenerate
• Difficulty controlling movements
• Intellectual abilities gradually decline
Dopamine
• Secretion stimulated by amphetamines, or
“speed”
• Large doses can produce symptoms
resembling schizophrenia
• Important in nuclei that control intentional
movements
• Important in other centers of diencephalon
and cerebrum
Aging
• Anatomical and physiological changes
begin after maturity (age 30)
• Accumulate over time
• 85% of people over age 65 have changes
in mental performance and CNS function
Reduction in Brain Size
and Weight
• Decrease in volume of cerebral cortex
• Narrower gyri and wider sulci
• Larger subarachnoid space
Reduction in Number of
Neurons
• Brain shrinkage linked to loss of cortical
neurons
• No neuronal loss in brain stem nuclei
Decrease in Blood Flow to Brain
• Arteriosclerosis:
– fatty deposits in walls of blood vessels
– reduce blood flow through arteries
– increase chances of rupture
• Cerebrovascular accident (CVA), or
stroke:
– may damage surrounding neural tissue
Intracellular and Extracellular
Changes in CNS Neurons
• Neurons in brain accumulate abnormal
intracellular deposits
• Including lipofuscin and neurofibrillary
tangles
Incapacitation
• 85% of elderly population develops
changes that do not interfere with abilities
• Some individuals become incapacitated by
progressive CNS changes
Senility
• Also called senile dementia
• Degenerative changes:
– memory loss
– anterograde amnesia
– emotional disturbances
• Alzheimer’s disease is most common
That’s it
(phew!)